1. Field of the Invention
This invention relates to an air conditioner with a function for protecting an electric circuit in an outdoor unit and, more particularly, to an air conditioner having a high-pressure protective release function.
2. Description of the Related Art
An air conditioner comprising a heat pump type refrigeration cycle divided into indoor and outdoor units as shown in FIG. 6, and capable of performing cooling and heating operations is known as a conventional air conditioner.
In the air conditioner shown in FIG. 6, reference numeral 1 denotes a variable-capacity compressor in an outdoor unit (ODU). Compressor 1 sequentially communicates with four-way valve 2, outdoor heat exchanger 3, and a decompressor, e.g., expansion valve 24, and with indoor heat exchanger 5 and the like in an indoor unit (IDU), thereby constituting the heat pump type refrigeration cycle.
According to such an air conditioner, in a cooling operation, a refrigerant is supplied in directions indicated by solid arrows in FIG. 6 to form a cooling cycle. In this case, outdoor and indoor heat exchangers 3 and 5 respectively serve as a condenser and an evaporator.
In a heating operation, a refrigerant is supplied in directions indicated by broken arrows in FIG. 6 upon switching operation of four-way valve 2 to form a heating cycle. In this case, indoor and outdoor heat exchangers 5 and 3 respectively serve as a condenser and an evaporator.
Compressor 1 receives operating power from inverter 6.
Outdoor fan 7 is arranged near outdoor heat exchanger 3.
Indoor fan 8 and indoor temperature sensor (inlet air temperature sensor) 9 are arranged near indoor heat exchanger 5. In addition, heat exchange temperature sensor 10 is arranged near indoor heat exchanger 5.
Furthermore, as shown in FIG. 7, outdoor unit ODU has inlet and outlet ports 12 and 13. Outdoor unit ODU draws outside air in through inlet port 12 upon operation of outdoor fan 7, and cools inverter 6 with part of the in-drawn air and heat-exchanges the residual of the drawn air by means of outdoor heat exchanger 3. Outdoor unit ODU then discharges the heat-exchanged air from outlet port 13.
During a cooling or heating operation, the output frequency (to be referred to as an operating frequency hereinafter) of inverter 6 is controlled in accordance with the difference between a preset indoor temperature and a temperature detected by indoor temperature sensor 9. With this operation, compressor 1 obtains an optimum capacity corresponding to an air-conditioning load. Hence, increased comfort of the user, as well as an energy saving effect can be achieved by the air conditioner.
Note that when the temperature of indoor heat exchanger 5 detected by heat exchange temperature sensor 10 exceeds a given value, which is set as an operating temperature of heat exchange temperature sensor 10 so as to keep the pressure of a high-pressure refrigerant below a predetermined value during a heating operation, the operating frequency of compressor 1 is gradually decreased, and at the same time, operation of outdoor fan 7 is immediately stopped. This control operation is called high-pressure protective release, and is an important function to prevent unnecessary interruptions of the compressor due to an abnormal increase in pressure of the high-pressure refrigeration side of a refrigeration cycle.
Outdoor fan 7, however, is also used to cool electric parts such as inverter 6 in outdoor unit ODU, as shown in FIG. 6. For this reason, if the above-described high-pressure protective release operation is prolonged and outdoor fan 7 does not resume operation, failures may occur in the electric parts such as inverter 6.
Such an arrangement, therefore, tends to degrade reliability of an air conditioner having a high-pressure protective release function, and hence is not preferable.